Update README.rst

Author: yuan-bwn

README.rst

@@ -157,16 +157,16 @@ Using this SDK you can create steps, chain them together to create a workflow,
 create that workflow in AWS Step Functions, and execute the workflow in the
 AWS cloud.
 
-.. image:: https://github.com/aws/aws-step-functions-data-science-sdk-python/raw/master/doc/images/create.png
- :scale: 50 %
- :alt: Create a workflow in AWS Step Functions
+.. image:: https://raw.githubusercontent.com/aws/aws-step-functions-data-science-sdk-python/master/doc/images/create.png
+  :width: 400
+  :alt: Create a workflow in AWS Step Functions
 
 Once you have created your workflow in AWS Step Functions, you can execute that
 workflow in Step Functions, in the AWS cloud.
 
-.. image:: https://github.com/aws/aws-step-functions-data-science-sdk-python/raw/master/doc/images/execute.png
- :scale: 50 %
- :alt: Start a workflow in AWS Step Functions
+.. image:: https://raw.githubusercontent.com/aws/aws-step-functions-data-science-sdk-python/master/doc/images/execute.png
+  :width: 400
+  :alt: Start a workflow in AWS Step Functions
 
 Step Functions creates workflows out of steps called `States <https://docs.aws.amazon.com/step-functions/latest/dg/concepts-states.html>`__,
 and expresses that workflow in the `Amazon States Language <https://docs.aws.amazon.com/step-functions/latest/dg/concepts-amazon-states-language.html>`__.